X-ray tube



1,621,852 March 1927' M. MORRISON X-RAY TUBE Filed March 1, 1922INYENTOR MONTFORD MORRISON ATTORNEY Patented Mar. 22, 1927..

MONTFOBD'MDBRISON, OFNEW" YORK, 1 T. Y.

Application filed March 1, 1922.

My invention relates to high-tension electrical devices and moreparticularly it re lates to certain improvements in apparatus fortliegenerationof Roentgen or X-rays.

An object of the invention herein described is the provision of an X-raytube capable of withstanding higher potentials.

Another object of the present invention is the provision of "an X-raydevice which will afford greater safety to a patient exposedto'theaictionof the same.

Other objects will be'inferred from a reading of the followingspecification. 7

As the K ra y art advances it is found desirable to constructincreasingly 'more powerful X-ray generating units. One way ofgenerating nore powerful 'X-rays is by the application of highervoltages to the terminals of :an X-ra'y device. In attempting, however,to operate X-ray tubes .at increasing'ly higher voltages at point hasbeen reached at which troubles have arisen to prohibit the use ofvoltages as high as is found desirable. @ne of these troubles has beenthe corona phenomena occurring at the terminals of the electrodes.

The occurrence of corona, as known, is brought about when theelectrostatic "flux density in the air exceeds a certain value. It isalso known that the flux density for a given potential difference isgreater the less the radius of curvature of the conductor. It willtherefore be appreciated that by making the terminals of the electrodesin an X-ray tube of such configuration that they will have large radiiof curvature, corona effects will be diminished. In lieu, therefore, ofelectrode terminals having a small radius of curvature, it is proposed,according to this invention to so construct the terminals that theyshall have no points of protuberances or small radii but shall be formedto have comparatively large radii of curvature.

The formation of corona is objectionable for the reason that there is aleakage of electricity from the conductors which the corona surrounds,which means that power is lost in this way. The effects of corona,however, are more objectionable from another standpoint than that of thepower loss, for the reason that in the regions where the corona appearsthe air is electrically broken down and ionized so that it becomes aconductor Serial lief-540,141.

ofelectricity, whereby a disruptivedischarge or spark is enabled tojumpfrom one electrode to the other. The sparking .or flash over thusoccurring of course diminishes, and hence limits, the penetrability ofthe ILrays and is therefore to be avoided. In addition to'the foregoing,other reasons may be cited why corona should be eliminated, such,form'enainple, as the prevention of the formation ofnit'ric acid and theconsequent corrosion of the conductors on which the corona forms.

The fpr ovision of electric terminals hav- 1ng large radii of curvatureas proposed by this invention is especially valuable in X-ray tubeconstructions wherein it is desired to remove the electrodes as remotelyas possible from the patient subject to the action ofthe X-ra-y tube. Aconstruction in which theclectrodcs are thus remotely removed is verydesirable'since inthe past, accidents of a serious and even fatal naturehave resulted from X-ray tubes having a construction easily permittingpersonalcontact with both electrodes. The usual form of commercialtubeheretofore in use has consisted of spherical bulb having oppositelyextending arms through which the electrodes pass. Such constructionusually places the axis of ithejelgectrodesin a plane parallel to thebody of a patient. According to the present invention, however, theelectrodes are directed away from a patient as remotely as practicableso as to avoid the danger of contact with the terminals which arecharged to a high potential. This construction has another advantage towhich attention will be hereinafter directed.

The accompanying drawing shows a side elevation of my improved tubeembodying illustrations of the features of my invention.

Referring to the drawing, a spherical glass bulb 1 encloses a cathode 2and an anode 3 which respectively pass longitudinally through, and aresealed to, diverging cylindrical arms l and 5. The cathode 2, as shownin this instance, consists partially of a refractory material 6 wountinto a helix and adapted to be heated electrically to iii-- candescencethrough its leading-in wires 7' and 8. The anode 3 may consist of atarget 16 having a face 11 and a conductor 12 leading to the target fromthe exterior of the bulb. Observing the position of the face of thetarget, from which X-rays emanate, it will be noted that the electrodesare positioned so as to be remote from the objective of the X-rays, afeature of this invention which provides a safer Xray tube.

At the upper extremities 14: and 15 of the arms 4.- and 5 respectively,preferably at the points Where the cathode and the anode emerge fromthese arms, terminals 16 and 17 are attached to the cathode 2 and theanode 3 respectively. The terminals 16 and 17 are, in this instance,shown as spheres having comparatively large radii of curvature,although, as previously stated, their configuration for the purpose ofthis invention may take other forms, provided the radii of curvature arecomparatively large. As previously set forth, the provision of terminalsof'the kind described are effective in preventing corona and inobviating flashover between the terminals and they are especiallyvaluable in a construction in which the electrodes are so positioned asto be relatively far removed from the objective of the X-rays.

The novel positioning of the electrodes according to this invention, inaddition to affording greater personal safety, affords an advantage inthe manufacture of the target of the tube. It is well known that thecommon form of X-ray target is necessarily beveled to properly directthe rays. In a tube of the present invention, however, a target whichneed not be beveled may be used and an advantage is thus gained in themanufacture of the tubes.

While I have herein described one embodiment of my invention it is to beunderstood that many modifications may be made therein but that thesemodifications are intended to be embraced in this invention ashereinafter claimed.

What is claimed is:

1. An X-ray tube comprising an evacuated envelope consisting of a mainchamber provided with auxiliary extensions therefrom of substantiallyequal length, with approximately 90 therebetween, electrodes extendingapproximately along the axes of the ex tensions, converging toward eachother and each provided with an external, substantially spherical,terminal of large size, for avoiding corona effects therebetween.

2. An X-ray device comprising an evacuated envelope formed as a mainsubstantially spherical chamber with two substantially cylindricalextensions therefrom of. substantially equal length, subtending an angleof approximately 90 therebetween, a cathode in one of said extensionsand an anode in the other, converging toward each other and eachprovided with an external terminal with all its exterior surface havinglarge radii of curvature for the purpose of avoiding corona effectstherebetween, when high voltage is applied to the device.

3. An X-ray tube comprising an envelope, electrodes disposed within saidenvelope and having terminals extending outside of said envelope, saidterminals being of such shape and form as to reduce corona effects.

4. An X-ray tube comprising an envelope, a plurality of electrodesdisposed within said envelope and having terminal portions extendingbeyond the exterior surface of said envelope, said terminal portionshaving such a large radii of curvature as to substantially preventcorona effects when high voltage is applied to said tube.

' In testimony whereof, I have hereunto subscribed my name this 27th dayof February 1922.

MONTFORD MORRISON.

